The standardization of the LTE (Long Term Evolution) system, which is the 3.9th generation wireless communication system for mobile phones, has been substantially completed. Recently, the standardization of LTE-A (LTE-Advanced), which is a development of the LTE system, has been progressing as the 4th generation wireless communication system (also referred to as IMT-A or the like).
Generally, in uplink of a mobile communication system (communication from a mobile station apparatus to a base station apparatus), a mobile station apparatus serves as a transmitter, and thus a single carrier scheme is considered to be effective in which power usage efficiency of an amplifier can be kept high with limited transmit power and peak power is low (in LTE, an SC-FDMA (Single Carrier Frequency Division Multiple Access) scheme is adopted). SC-FDMA is also referred to as DFT-S-OFDM (Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing) or DFT-precoded OFDM.
In LTE-A, to further enhance frequency usage efficiency, it has been determined to newly support an access scheme which is referred to as Clustered DFT-S-OFDM (also referred to as DSC (Dynamic Spectrum Control), SC-ASA (Single Carrier Adaptive Spectrum Allocation), or the like), in which an SC-FDMA spectrum is divided into clusters constituted by a plurality of sub-carriers, and the individual clusters are allocated to certain frequencies along a frequency axis, for a mobile station apparatus having sufficient transmit power.
Furthermore, spectrum-overlapped resource management (SORM) has been suggested, in which a higher priority is given to channel characteristics and overlap on a receiving side is allowed at the time of spectrum allocation for individual mobile station apparatuses, without performing frequency division multiplexing, under the assumption that turbo equalization is used for reception processing (for example, PTL 1).
In SORM, frequency resources are allocated to individual mobile station apparatuses while giving a higher priority to channel characteristics. Therefore, signals from different mobile station apparatuses are received by a base station apparatus with the signals being partially overlapped one on another. The base station apparatus that is capable of detecting all transmit data from the individual mobile station apparatuses is capable of gradually detecting the signals by using detection results (soft estimates) about all the mobile station apparatuses connected thereto.
In addition, NPL 1 discloses a technique in which a base station apparatus causes some of frequency resources to be overlapped, thereby saving the frequency resources of an entire system band. With this technique, the base station apparatus is capable of allocating more frequency resources and enhancing the overall frequency usage efficiency.